Effects of spatial structure on stock assessment estimates of biomass and productivity for Yelloweye rockfish (Sebastes ruberrimus) in British Columbia

Ignoring the underlying structure of populations can lead to sub-optimal management of fisheries resources. I examined the influence of spatial population structure assumptions on stock assessment estimates of biomass and productivity for Yelloweye rockfish in British Columbia, Canada. Delay-difference assessment models were fit to different scenarios in which discrete stocks were delineated at successively smaller spatial scales. My results show that, in some scenarios, uncertainty in stock assessment outputs was no greater at finer spatial scales than for the aggregate stock. There was also evidence of differences in stock status at finer scales, suggesting that it might be worthwhile to establish methods for tracking Yelloweye on a finer spatial scale. Comparisons between the aggregated, coast-wide stock, and disaggregated north and south assessments would allow tracking of any differences in responses to management, providing additional certainty regarding management options and potentially lead to improved outcomes for the species.